Hello,
My current theory is that the SEPM is erroring because you're trying to do two things to the same setting.
This issue happens at different places and due to several reasons.
Few Checks to perform.
1) Check disk space for the database. Free some disk space (if possible)
2) Log into SEPM ( after restarting service)
3) Make some/any changes to clients/policies/settings
Try again, whatever you were trying to do.